1. Field of the Invention
The invention relates to a golf club head and, more particularly, to a golf club head having a face with projections extending outwardly therefrom for contacting a golf ball.
2. Discussion of the Related Art and Summary of the Invention
The faceplates or front faces of many golf club heads often have striations or other protrusions which extend outward from a base surface of the faceplate. Golf club manufacturers have used the striations or protrusions to delineate the strike area of the club head and to vary the friction between the strike face of the club head and the golf ball and thereby cause the ball to spin at impact.
The Applicant has determined that the use of protrusions on the club strike face may also be used to vary the "feel" of the club by varying the amount of contact area between the club head and the golf ball at impact. The "feel" of the club generally relates to the feeling that the club confers to the player's hands upon impact of the club head with the golf ball. By changing the size and shape of the projections, the amount of contact area between the club head and the golf ball may be reduced or enlarged. In general, it is desirable to configure the protrusions such that the ball only contacts the tips of the protrusions at impact, rather than also contacting the base surface of the protrusions, so that the amount of contact area between the golf ball and the club is not overly increased.
Depending on the particular club type, however, the optimal amount of contact area between the tips of the protrusions and the golf ball may vary. For example, with certain clubs types, such as woods and irons, it is generally desirable to increase the amount of contact area, such as to enhance the level of friction between the club head and the golf ball at impact. This may be accomplished, for example, by using projections that are sized to fit within the golf ball dimples at impact. However, the projections of prior club heads are not configured to enter the dimples of the golf ball and thus are limited in their contact area to the smooth surfaces of the ball. As the dimples cover most of the ball surface, the contact area with such prior art club head faceplates is substantially limited. This limits the striking force on the ball and lessens the driving distance accordingly. Also with the faceplate of the club head only contacting the smooth surfaces of the ball, there is a strong possibility of hitting a slice or hook shot.
On the other hand, the desired amount of contact area between the club face and the golf ball is different for putters than for irons and woods, as putters are used in different environments and with a different swinging style than irons and woods. When putting a golf ball, golfers generally use a pendulum-type motion with a putter head to strike a golf ball with the front face of the putter head and propel the golf ball towards a hole in the green. As the putter head strikes the golf ball, a portion of the front face of the putter head contacts the golf ball for a brief period of time and transfers the momentum of the putter head to the golf ball. The amount of time that the putter head remains in contact with the golf ball during the putting stroke is referred to as the "dwell time."
Golf club manufacturers are attempting to create putters that transfer sufficient momentum to the golf ball while also providing an improved feel for the player. The feel of the putter head is primarily a function of the spring constant (k) of the putter face. The spring constant is generally determined by the Young's modulus of the material, as well as the amount of surface area on the putter face that actually contacts the ball during the putting stroke.
To improve the feel of the putter, golf club manufacturers are providing the putter head with soft plastic inserts that are mounted on the face of the putter head. The plastic inserts are mainly directed toward improving the feel of the putter through the use of low modulus material. U.S. Pat. No. 4,928,965 and U.S. Pat. No. 5,575,472 are examples of golf putters having soft plastic face inserts. The plastic inserts generally have a low Young's modulus to improve the feel of the putter, but unfortunately also presents certain disadvantages. In particular, plastic inserts have a tendency to lower the sound when the club impacts the ball which causes a lack of audio feedback to the player.
The Applicant has observed that the feel of the putter head may be improved by lowering the spring constant of the putter head. This can be accomplished by lowering the total area of the putter face that contacts the ball during the putting stroke. That is, the "contact area" of the putter face on the golf ball is reduced. Desirably, while the contact area of the putter head is reduced to improve feel, there is still maintained a sufficient amount of contact between the putter face and the golf ball to retain precision and control of the putt. This may be accomplished by manufacturing the putter face with a unique structural design comprising projections that extend outward from the putter face to define a reduced contact area.
In the past, golf club manufacturers have provided projections on the face of golf clubs to impart certain characteristics to the ball upon impact. On the other hand, most of these designs are directed to high impact clubs, such as the irons and woods. For example, Japanese Patent No. 0023877 to Shirayanagi discloses a golf club head having a face plate upon which a plurality of small synthetic resin bumps are formed. The Shirayanagi patent is directed toward a high impact club, rather than a putter. The primary purpose of the face plate is to provide high friction between the ball and the face of the club. Additionally, the inclined orientation of the Shirayanagi face and the bumps on the face promote the transfer of spin to the ball, which is from above a certain level undesirable for a putter. The bumps on the face are also small and resilient so that only a very small deformation of the golf ball causes the ball to wrap around the bumps and contact additional club face. The contact area of the Shirayanagi club is thus not significantly reduced.
British Patent No. 4301 discloses a golf club head for an iron-type club. The head includes hemispherical or conical protuberances which are formed on the club face. The protuberances produce a certain level of roughness to the head upon impact with a golf ball. Unfortunately, this increases the amount of friction between the club face and the ball, which results in ball spin and would lead, if the protuberances were applied to a putter club, to an unpredictable putt.
When projections have been used in connection with putters, the projections unfortunately do not have the proper structure to effectively improve the feel and control of a putter. For example, U.S. Pat. No. 4,964,641 to Miesch et al. discloses a golf club with a machined face. The face of the Miesch club includes a plurality of contiguous pyramidal-shaped elements having sharp tips which collectively form the contact face of the club. However, because the tips of the pyramidal-shaped elements are sharp points, the contact area of the Miesch golf club is extremely small, which causes the ball trajectory to be less controllable. The lack of sufficient contact area may also result in inconsistencies between putting strokes, since the impact of the club upon the ball varies significantly depending upon the location and the angle of the putter face with the ball. Additionally, the sharp ends of the pyramidal structures increase the friction between the club face and the ball, which can result in the club conferring too much spin to the ball so that the golf ball trajectories are unusual and unpredictable. None of the above-described references provides a putter head which improves the feel of the putter at impact while also providing satisfactory levels of control and consistency when putting a golf ball.
Thus, there is a need for a golf club that optimizes the contact area between the strike face and the golf ball at impact. The club desirably has protrusions that are configured to prevent the ball from contacting the base surface of the club face at impact. In the case of woods and irons, the club desirably facilitates the control of the driving action of a golf club and has a faceplate which engages a greater surface area of a golf ball, such as through the use of striker projections which engage the dimples of the club at impact. In the case of a putter, the club head desirably provides improved feel by reducing the amount of contact area at impact, while maintaining a sufficient level of contact area so that control and precision of the putt does not suffer.
The aforementioned needs are satisfied by the present invention. One aspect of the invention relates to a club head comprising a main body defining a strike portion sized to strike a golf ball. The strike portion comprises a main surface and a plurality of projections integrally formed with and extending outward from the main surface. The projections are spaced apart and define individual flat end surfaces for contacting the surface of a golf ball. The flat end surfaces extend along a plane substantially parallel to the main surface, wherein the projections are stiff enough to prevent a golf ball from contacting the main surface when the club head strikes the golf ball.
Desirably, the flat end surfaces collectively define an area that is between 15%-45% of the area of the strike portion. The density of the projections on the strike portion is desirably at least 30 projections per square inch and the projections are desirably uniformly distributed on the strike portion to form a plurality of interlinked hexagonal patterns. In one embodiment, each of the plurality of projections is separated from adjacent other of the plurality of projections by a distance between 0.020 and 0.078 inches.
In one embodiment, the end surfaces of the projections are desirably circular and have a diameter of approximately 0.020-0.078 inches. The projections desirably have a length of at least approximately 0.010 inches and preferably approximately 0.010-0.045 inches. The projections desirably extend in a direction substantially normal to a plane defined by the main surface of the front face. In another embodiment, the end surfaces of the projections each define an elliptical shape or a polygonal shape.
Desirably, the club head defines a lower edge and an upper edge, and the projections are uniformly spaced from the lower edge to the upper edge. The end surfaces of the projections located within a lateral region of the strike portion are desirably larger than the end surfaces of the projections located within a central region of the strike portion.
In another embodiment, the main body further comprises a face insert sized to fit within a recess, wherein the projections extend outward from the face insert. The front surface and the projections may be integrally formed of a metallic material.
In another aspect of the invention, there is disclosed a club head comprising a main body defining a front face. Desirably, a plurality of projections extending from the front face, the ends of the projections defining a plurality of individual contact surfaces for striking a golf ball. The plurality of projections prevent a golf ball from contacting the front face thereby resulting in a decrease of the golf ball general contact area.
In yet another aspect of the invention, there is disclosed a club head having projections which are distributed over the striking surface of the faceplate and extend substantially normally from a plane parallel to the striking surface. The distal ends of the projections form a striking surface for driving a golf ball. These projections are of a size which permits them to enter the dimples of the golf ball. Thus, the striking surface includes not only the smooth portions of the ball but also the surface area covered by the dimples. This provides a substantially greater contact surface between the club head and the ball. Further, the striker projections which enter the dimples are frictionally engaged by the dimple walls to make for a straighter shot. In addition, this engagement tends to give the ball spin for a controlled roll. In the case of sand irons, more lift can be attained with differences in the sizes of the projections placed in different positions on the face thereby contributing to more or less loft, as may be desired.
In one embodiment, the striker projections are preferably cylindrical or oval in configuration and preferably are smooth on their tops. The size of the projections are preferably small enough so that they can fit within most ball dimples. For durability the projections are generally made solid but can be made hollow to save weight. The projections are desirably dimensioned and positioned on the faceplate to avoid damage to the ball and to as closely as possible align with ball dimples.
In one embodiment, all of the clubs in a set employ the same basic striker projection design which is directed to make for a solid hit. It has been found that forged irons produce truer online shots with a positive feel on impact. The long irons tend to give straighter shots adding distance while the short irons tend to have greater accuracy. The sand irons are afforded more lift and back spin due to the action of the projections on the dimples. Differences in the size of the projections on different portions of the faceplate can contribute to differences in the amount of loft and spin obtained.